I was playing on a creative single world with this mod in a mod pack and had noticed the chess boards and wanted to experiment with them. I was using the Golden Chess Board and I had noticed that I could move infinitely as long as I didn't close the board, but, when I closed and reopened the board I could control the black pieces instead, similarly I could infinite move them as well till I closed the board. After noticing this I spam opened and closed the Golden Chess Board and the world crashed after a while. I tried to re-enter the world and as soon as it loaded it showed the saving world screen kicking me right back out.
crash-2022-06-27_13.29.40-client.txt

Thanks for posting the issue.

Well, my first thoughts are that I should be a bit more cautious about how I deal with corrupted data. The Golden Chess Board must have a king, by definition, and that error comes from it not having a king. It is reasonable that I make an issue to make it fail more softly. Why the NBT is corrupt is another matter... which modpack are you using? Is there a curseforge link for convenience? I'll look into the spamming, but that shouldn't be able to corrupt stuff on its own.

Will deal with the soft fail in #92

The modpack isn't on curseforge yet as the creator is still tweaking the fine details, but I can link the discord server with the modpack on it for you.